The size and mass evolution of the massive galaxies over cosmic time

TL;DR

This paper reviews the structural evolution of massive galaxies over cosmic time, focusing on mechanisms like minor mergers and the challenges in observationally confirming these processes.

Contribution

It provides a comprehensive review of the current understanding and open questions regarding the size and mass evolution of massive galaxies.

Findings

Minor mergers likely drive size growth of massive galaxies

Satellite galaxy counts are insufficient to fully explain growth

Presence of compact massive galaxies complicates evolutionary models

Abstract

Once understood as the paradigm of passively evolving objects, the discovery that massive galaxies experienced an enormous structural evolution in the last ten billion years has opened an active line of research. The most significant pending question in this field is the following: which mechanism has made galaxies to grow largely in size without altering their stellar populations properties dramatically? The most viable explanation is that massive galaxies have undergone a significant number of minor mergers which have deposited most of their material in the outer regions of the massive galaxies. This scenario, although appealing, is still far from be observationally proved since the number of satellite galaxies surrounding the massive objects appears insufficient at all redshifts. The presence also of a population of nearby massive compact galaxies with mixture stellar properties is another piece of the puzzle that still does not nicely fit within a comprehensive scheme. I will review these and other intriguing properties of the massive galaxies in this contribution.